Circadian rhythms optimize health by coordinating the timing of physiological processes to match predictable daily environmental challenges. The circadian rhythm of body temperature is thought to be an important modulator of molecular clocks in peripheral tissues, but how daily temperature cycles impact physiological function is unclear. Here, we examined the effect of constant (25°C, TCON) and cycling (28°C/22°C during light/dark, TCYC) temperature paradigms on lifespan of Drosophila melanogaster, and the expression of clock genes, Heat shock protein 83 (Hsp83), Frost (Fst), and Senescence-associated protein 30 (smp-30). Male and female Drosophila housed at TCYC had longer median lifespans than those housed at TCON. TCYC induced robust Hsp83 rhythms and rescued the age-related decrease in smp-30 expression that was observed in flies at TCON, potentially indicating an increased capacity to cope with age-related cellular stress. Ageing under TCON led to a decrease in the amplitude of expression of all clock genes in the bodies of male flies, except for cyc, which was non-rhythmic, and for per and cry in female flies. Strikingly, housing under TCYC conditions rescued the age-related decrease in amplitude of all clock genes, and generated rhythmicity in cyc expression, in the male flies, but not the female flies. The results suggest that ambient temperature rhythms modulate Drosophila lifespan, and that the amplitude of clock gene expression in peripheral body clocks may be a potential link between temperature rhythms and longevity in male Drosophila. Longevity due to TCYC appeared predominantly independent of clock gene amplitude in female Drosophila.
Spatial Variability in the Effect of High Ambient Temperature on Mortality: An Analysis at Municipality Level within the Greater Athens Area
